Incorrect `mimo-v2.6-flash-free` context length

[GT-610]

This model supports 1M (1048576) context, but is labeled as 262K. However this won't impact actual usage.

Anyway hope this would be fixed soon.

[GT-610]

Also output limit is incorrect: should be 131072, but current limit might be bigger than this number. Often reached output limit while using.

[GT-610]

#18 should fix this. I've checked and tried to patch locally.